Aspergillus fumigatus galactomannan (GM) was found to consist of a core alpha (1 greater than 2) manner and Beta (1 greater than 5) or Beta (1 greater than 6) galactose side chains. Hapten inhibition studies found that rabbit antibody bound only the side chains. Rapid hepatic clearance of intravenously injected GM occurred because of mannose-receptor mediated endocytosis by Kupffer cells. The hepatocyte galactose-receptor failed to bind GM because galactose is in a furanose and not a pyranose configuration. Normal volunteers immunized 7 days earlier with polysaccharide of type A Cryptococcus neoformans had peripheral blood B lymphocytes which spontaneously secreted anticrytococcal antibody. Polyclonal stimulation by mitogens decreased antibody secretion at this time but promoted secretion at 10-14 days postimmunization. Ketoconazole, a new oral antifungal agent, was effective in blastomycosis and histoplasmosis. An improved HPLC assay correlated with bioassay up to serum concentrations of 10 Mug/ml.